1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus. This invention particularly relates to a radiation image read-out method and apparatus, wherein light emitted by a stimulable phosphor sheet is detected with a line sensor or an area sensor.
2. Description of the Prior Art
It has been proposed to use stimulable phosphors in radiation image recording and reproducing systems. Specifically, a radiation image of an object, such as a human body, is recorded on a stimulable phosphor sheet, which comprises a substrate and a layer of the stimulable phosphor overlaid on the substrate. Stimulating rays, such as a laser beam, are deflected and caused to scan pixels in the radiation image, which has been stored on the stimulable phosphor sheet, one after another. The stimulating rays cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted successively from the pixels in the radiation image having been stored on the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal by photoelectric read-out means. The stimulable phosphor sheet, from which the image signal has been detected, is then exposed to erasing light, and radiation energy remaining thereon is thereby released.
The image signal, which has been obtained from the radiation image recording and reproducing systems, is then subjected to image processing, such as gradation processing and processing in the frequency domain, such that a visible radiation image, which has good image quality and can serve as an effective tool in, particularly, the efficient and accurate diagnosis of an illness, can be obtained. The image signal having been obtained from the image processing is utilized for reproducing a visible image for diagnosis, or the like, on film or on a high resolution cathode ray tube (CRT) display device. The stimulable phosphor sheet, from which residual radiation energy has been released with the erasing light, can be used again for the recording of a radiation image.
Novel radiation image read-out apparatuses for use in the radiation image recording and reproducing systems described above have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540. In the proposed radiation image read-out apparatuses, from the point of view of keeping the emitted light detection time short, reducing the size of the apparatus, and keeping the cost low, a line light source for irradiating linear stimulating rays onto a stimulable phosphor sheet is utilized as a stimulating ray source, and a line sensor comprising a plurality of photoelectric conversions devices arrayed along the length direction of a linear area of the stimulable phosphor sheet, onto which the stimulating rays are identified by the line light source, is utilized as photoelectric read-out means. Also, the proposed radiation image read-out apparatuses comprise scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction, which is approximately normal to the length direction of the linear area of the stimulable phosphor sheet.
FIGS. 6A, 6B, and 6C are explanatory views showing relationship between a line width of light emitted by a stimulable phosphor sheet and a photoelectric conversion device constituting a conventional line sensor. In FIG. 6A, a beam width (a line width) of light M emitted linearly (i.e., in a linear pattern extending along a direction normal to the plane of the sheet of FIG. 6A) by a stimulable phosphor sheet 50 is represented by dM. FIGS. 6B and 6C show the distribution of the intensity of the emitted light M along the line width direction. As illustrated in FIG. 6B, in cases where the emitted light M is collected by a line sensor, in which a light receiving width dP of each photoelectric conversion device is smaller than the line width dM, the light collecting efficiency cannot be kept high. Also, as illustrated in FIG. 6C, in cases where the emitted light M is collected by a line sensor, in which the light receiving width dP of each photoelectric conversion device is approximately equal to the line width dM, the light collecting efficiency can be kept high. However, in such cases, since the size of each pixel is large, the problems occur in that the resolution cannot be kept high. (The same problems occur also when each photoelectric conversion device has a rectangular shape such that the length along the line width direction may be larger than the length in the direction along which the line extends.)
The emitted light M has the intensity distribution shown in FIGS. 6B and 6C since the line width of the stimulating rays L becomes large before impinging upon the stimulable phosphor sheet 50, since, as illustrated in FIGS. 3A and 3B, the stimulating rays L of a line width dL ( less than dM) having entered into the stimulable phosphor sheet 50 are scattered in the stimulable phosphor sheet 50, and since the emitted light M having occurred in the stimulable phosphor sheet 50 is scattered in the stimulable phosphor sheet 50 before being radiated out of the surface of the stimulable phosphor sheet 50.
The primary object of the present invention is to provide a radiation image read-out method, wherein desired resolution is obtained and the efficiency, with which light emitted by a stimulable phosphor sheet is collected by a line sensor, is kept high.
Another object of the present invention is to provide a radiation image read-out method, wherein directivity of stimulating rays radiated out of a line light source is kept high, the intensity of the radiated stimulating rays is kept high, and an image having a high signal-to-noise ratio is thereby obtained.
A further object of the present invention is to provide a radiation image read-out method, which enables a radiation image read-out apparatus to be formed in a smaller outer shape than that of a conventional radiation image read-out apparatus.
A still further object of the present invention is to provide a radiation image read-out method, wherein a line light source and a line sensor are utilized and an image signal appropriate for reproduction of a visible radiation image having a high signal-to-noise ratio is capable of being obtained.
Another object of the present invention is to provide a radiation image read-out method, wherein a line light source and a line sensor are utilized and image signals for energy subtraction processing are capable of being obtained easily.
A further object of the present invention is to provide a radiation image read-out method, wherein light emitted by a stimulable phosphor sheet is detected quickly and accurately as with a photomultiplier, the efficiency with which the weak emitted light is utilized is enhanced, and an image signal appropriate for reproduction of a visible radiation image having a high signal-to-noise ratio is capable of being obtained.
The specific object of the present invention is to provide apparatuses for carrying out the radiation image read-out methods.
A first radiation image read-out method in accordance with the present invention is characterized by detecting light, which is emitted from a linear area of a stimulable phosphor sheet, with a line sensor comprising a plurality of photoelectric conversion devices arrayed along two-dimensional directions, performing operation processing on outputs of the photoelectric conversion devices, which outputs have been obtained at respective scanning positions and correspond to an identical site on the stimulable phosphor sheet, and thereby enhancing a light collecting efficiency.
Specifically, the present invention provides a first radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of photoelectric conversion device arrayed along each of a length direction (i.e., a major axis direction) of the linear area of the stimulable phosphor sheet and a direction (i.e., a minor axis direction) normal to the length direction, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet,
iv) successively reading outputs of the line sensor in accordance with the movement, and
v) performing operation processing on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet.
As the line sensor, an amorphous silicon sensor, a charge coupled device (CCD) image sensor, a CCD image sensor with back illuminator, a metal oxide semiconductor (MOS) image sensor, or the like, may be employed. The line sensor may comprise a plurality of sensor chips (CCD image sensor chips, MOS image sensor chips, or the like) arrayed in a straight line or in a zigzag pattern along the length direction of the linear area of the stimulable phosphor sheet. Each of the sensor chips may comprise a plurality of photoelectric conversion devices arrayed in two-dimensional directions and in a matrix-like pattern or in a zigzag pattern.
In the first radiation image read-out method in accordance with the present invention, as the line light source, a fluorescent lamp, a cold cathode fluorescent lamp, a light emitting diode (LED) array, or the like, may be employed. The line light source is not limited to a light source having a linear shape as in the fluorescent lamp and may be one of various other light sources, such as board area lasers (e.g., a board area semiconductor laser) and electroluminescence (EL) devices, which irradiate one-dimensional stimulating rays onto the surface of the stimulable phosphor sheet. The LED array of the broad area laser should preferably be employed as the line light source, and a cylindrical lens, or the like, for suppressing spread of the stimulating rays to the direction (i.e., the minor axis direction), which is normal to the length direction (i.e., the major axis direction) of the line of the stimulating rays, such that the stimulating rays having been radiated out of the light source may take on the form of the linear stimulating rays on the source of the stimulable phosphor sheet.
The stimulating rays may be radiated continuously out of the line light source or may be pulsed stimulating rays radiated intermittently out of the line light source. From the point of view of reducing noise, the stimulating rays should preferably be pulsed stimulating rays having high intensity.
The length of the irradiation region of the stimulating rays, which have been radiated out of the line light source, on the stimulable phosphor sheet, the length being taken along the major axis direction, should preferably be equal to or longer than the length of one side of an effective image storing region of the stimulable phosphor sheet. In cases where the length of the irradiation region of the stimulating rays on the stimulable phosphor sheet is longer than the length of one side of the effective image storing region of the stimulable phosphor sheet, the stimulating rays may be irradiated from an oblique angle with respect to the side of the effective image storing region of the stimulable phosphor sheet.
In order for the degree of convergence of the stimulating rays, which has been radiated out of the line light source, on the stimulable phosphor sheet to be enhanced, the aforesaid cylindrical lens, a slit, a SELFOC lens (rod lens) array, a fluorescent light guiding sheet, an optical fiber bundle, or the like, or a combination of two or more of the above-enumerated elements should preferably be located between the line light source and the stimulable phosphor sheet. In cases where the optimum secondary stimulation wavelength for the stimulable phosphor sheet is approximately 600 nm, the fluorescent light guiding sheet should preferably contain Eu3+ (luminescence center) as an activator of a fluorescent substance and should preferably be constituted of a glass or polymeric medium.
The beam width of the stimulating rays, which have been radiated out of the line source, on the stimulable phosphor sheet should preferably fall within the range of 10 xcexcm to 4,000 xcexcm.
In order for the degree of convergence of the light, which is emitted from respective areas of the stimulable phosphor sheet, on the line sensor to be enhanced, a distributed index lens array, such as a SELFOC lens array or a rod lens array, constituted of an image forming system in which an object surface and an image surface correspond to each other in one-to-one relationship, a cylindrical lens, a slit, an optical fiber bundle, or the like, or a combination of two or more of the above-enumerated elements should preferably be located between the stimulable phosphor sheet and the line sensor.
A stimulating ray cut-off filter (a sharp cut-off filter or a band-pass filter) for transmitting only the light emitted by the stimulable phosphor sheet and filtering out the stimulating rays should preferably be located in the optical path of the emitted light between the stimulable phosphor sheet and the line sensor. In this manner, the stimulating rays should preferably be prevented from impinging upon the line sensor.
The size of a light receiving surface of each of the photoelectric conversion devices constituting the line sensor is set to be smaller than the beam width of the light, which is emitted by the stimulable phosphor sheet exposed to the stimulating rays having the beam width described above, on the light receiving surface of the line sensor. A plurality of the photoelectric conversion devices are arrayed along each of the length direction (i.e., the major axis direction) of the beam of the emitted light and the beam width direction (i.e., the minor axis direction). The length of the entire line sensor is set to be approximately equal to or longer than the length of the beam of the emitted light, and the width of the entire line sensor is set to be approximately equal to the beam width of the emitted light. The plurality of the photoelectric conversion devices may be arrayed in a matrix-like pattern such that they may stand in a straight line along each of the major axis direction and the minor axis direction. Alternatively, the photoelectric conversion devices may be arrayed such that they may stand in a straight line along the major axis direction and in a zigzag pattern along the minor axis direction. As another alternative, the photoelectric conversion devices may be arrayed such that they may stand in a straight line along the minor axis direction and in a zigzag pattern along the major axis direction. As a further alternative, the photoelectric conversion devices may be arrayed such that they may stand in a zigzag pattern along each of the major axis direction and the minor axis direction.
In cases where the line sensor is constituted of a large number of photoelectric conversion devices and there is the risk that adverse effects will occur with respect to a transfer rate, memory devices corresponding to the respective photoelectric conversion devices may be utilized, and an electric charge having been accumulated in each of the photoelectric conversion devices during a charge accumulation period may be stored in the corresponding memory device. In the next charge accumulation period, the electric charge may be read from each memory device. In this manner, the charge accumulation time may be prevented from becoming short due to an increase in the charge transfer time.
The number of the photoelectric conversion devices arrayed in each row along the major axis direction of the line sensor should preferably be at least 1,000. The length of the line sensor, as measured at the light receiving surface, should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet.
As will be understood from the specification, it should be noted that the term xe2x80x9cmoving a stimulable phosphor sheet with respect to a line light source and a line sensorxe2x80x9d as used herein means movement of the stimulable phosphor sheet relative to the line light source and the line sensor, and embraces the cases wherein the stimulable phosphor sheet is moved while the line light source and the line sensor are kept stationary, the cases wherein the line light source and the line sensor are moved while the stimulable phosphor sheet is kept stationary, and the cases wherein both the stimulable phosphor sheet and the line light source and the line sensor are moved. In cases where the light source and the line sensor are moved, they should be moved together with each other.
The term xe2x80x9cposition of movementxe2x80x9d as used herein means the position at the time at which the photoelectric detection is performed by the line sensor and does not mean the position through which the stimulable phosphor sheet or the line light source and the line sensor pass at any given instant during the movement.
The direction along which the stimulable phosphor sheet is moved with respect to the line light source and the line sensor (i.e., the direction different from the length direction of the exposed linear area of the stimulable phosphor sheet) should preferably be the direction approximately normal to the length direction of the exposed linear area of the stimulable phosphor sheet (i.e., should preferably be the minor axis direction). However, the direction along which the stimulable phosphor sheet is moved with respect to the line light source and the line sensor is not limited to the minor axis direction. For example, in cases where the lengths of the line light source and the line sensor are longer than one side of the stimulable phosphor sheet as described above, the stimulable phosphor sheet may be moved with respect to the line light source and the line sensor along an oblique direction with respect to the direction approximately normal to the length direction of the line light source and the line sensor or along a zigzag movement direction, such that approximately the entire surface of the stimulable phosphor sheet may be uniformly exposed to the stimulating rays.
The line light source and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. In cases where the line light source and the line sensor are located on opposite surface sides of the stimulable phosphor sheet, the substrate of the stimulable phosphor sheet, or the like, should be formed from a material permeable to the emitted light, such that the emitted light may permeate to the surface side of the stimulable phosphor sheet opposite to the surface on the stimulating ray incidence side.
The operation processing may be simple addition processing, weighted addition processing, or one of various other kinds of operation processing. In cases where the simple addition processing or the weighted addition processing is employed, addition means may be utilized as means for performing the operation processing.
Unless otherwise specified, the foregoing explanation of the first radiation image read-out method in accordance with the present invention also applies to various other radiation image read-out methods in accordance with the present invention, which will be described later.
A second radiation image read-out method in accordance with the present invention is characterized by reading out a radiation image, which has been stored on a stimulable phosphor sheet, by irradiating a linear laser beam, which has been radiated out of a broad area laser, onto the stimulable phosphor sheet.
Specifically, the present invention also provides a second radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and
iv) successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,
wherein the line light source is a broad area laser, which linearly radiates out the stimulating rays.
In the second radiation image read-out method in accordance with the present invention, the laser beam (i.e., the stimulating rays) may be radiated continuously out of the broad area laser or may be a pulsed beam radiated intermittently out of the broad area laser. From the point of view of reducing noise, the laser beam should preferably be a pulsed beam having high intensity. The wavelength of the laser beam produced by the broad area laser may fall within the range of 600 nm to 1,000 nm and should preferably fall within the range of 600 nm to 700 nm.
The length of the irradiation region of the laser beam, which has been radiated out of the broad area laser, on the stimulable phosphor sheet, the length being taken along the major axis direction, should preferably be equal to or longer than the length of one side of the effective image storing region of the stimulable phosphor sheet. In cases where the length of the irradiation region of the laser beam on the stimulable phosphor sheet is longer than the length of one side of the effective image storing region of the stimulable phosphor sheet, the laser beam may be irradiated from an oblique angle with respect to the side of the effective image storing region of the stimulable phosphor sheet.
The term xe2x80x9cbroad area laserxe2x80x9d as used herein means the laser which produces the laser beam in the linear pattern. The broad area laser should preferably be a broad area semiconductor laser constituted such that the length of the active layer along the major axis direction may fall within the range of 50 xcexcm to 1,000 xcexcm and the length of the active layer along the minor axis direction may fall within the range of 0.1 xcexcm to 10 xcexcm. However, the broad area laser employed in the second radiation image read-out method in accordance with the present invention is not limited to the broad area semiconductor laser and may be one of various other lasers which produces the laser beam in the linear pattern.
The line sensor employed in the second radiation image read-out method in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arranged along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the second radiation image read-out method in accordance with the present invention, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the operation processing may be performed on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet. In such cases, if the beam width of the light emitted by the stimulable phosphor sheet is larger than the width of each photoelectric conversion device, the line sensor as a whole can receive the emitted light over approximately the entire beam width. The operation processing, such as addition processing, is performed on the outputs of the photoelectric conversion devices, which outputs correspond to an identical site on the stimulable phosphor sheet. In this manner, the light receiving efficiency can be enhanced.
The number of the photoelectric conversion devices arrayed along the major axis direction of the line sensor should preferably be at least 1,000. The length of the line sensor, as measured at the light receiving surface, should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet. In cases where the length of the light receiving surface of the line sensor is longer than the length of one side of the effective image storing region of the stimulable phosphor sheet, the line sensor may be located obliquely with respect to the side of the effective image storing region of the stimulable phosphor sheet.
The broad area laser and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. In cases where the broad area laser and the line sensor are located on opposite surface sides of the stimulable phosphor sheet, the substrate of the stimulable phosphor sheet, or the like, should be formed from a material permeable to the emitted light, such that the emitted light may permeate to the surface side of the stimulable phosphor sheet opposite to the surface on the stimulating ray incidence side.
The stimulating rays irradiated to the stimulable phosphor sheet should preferably have an intensity falling within a range such that the power may not vary. In cases where the stimulating rays has an intensity falling within a range such that the power may vary, the intensity of the stimulating rays may be monitored with a monitoring means. When variation in power occurs, the broad area laser may be modulated with broad area laser modulating means more quickly than the photoelectric conversion speed of the photoelectric conversion devices such that the power of the broad area laser may become equal to a predetermine value. In this manner, adverse effects of power variation may be suppressed.
Third and fourth radiation image read-out methods in accordance with the present invention are characterized by overlapping part of an optical path of stimulating rays from a line light source to a stimulable phosphor sheet and part of an optical path of emitted light from the stimulable phosphor sheet to a line sensor, thereby reducing the space occupied by the optical paths and reducing the size of an entire radiation image read-out apparatus.
Specifically, the present invention further provides a third radiation image read-out method, comprising the steps of:
i) linearly radiating stimulating rays, which have been produced by a line light source,
ii) guiding the linear structure stimulating rays to an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray guiding means, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
iii) guiding light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with emitted light guiding means to a line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of the linear area of the stimulable phosphor sheet,
iv) receiving the emitted light with the line sensor, the received light being subjected to photoelectric conversion performed by the line sensor,
v) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet, and
vi) successively reading outputs of the line sensor in accordance with the movement,
wherein at least part of an optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of an optical path of the emitted light from the stimulable phosphor sheet to the line sensor overlap each other.
The term xe2x80x9coverlapping of optical pathsxe2x80x9d as used herein means that the center point of the stimulating rays and the center point of the emitted light overlap each other.
The overlapping of at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light should preferably be achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other.
As the stimulating ray guiding means, the aforesaid cylindrical lens, the slit, the SELFOC lens (rod lens) array, the aforesaid fluorescent light guiding sheet, the optical fiber bundle, a hot mirror, a cold mirror, or the like, or a combination of two or more of the above-enumerated elements may be employed.
The hot mirror is a dichroic mirror having been set so as to reflect the stimulating rays and to transmit the light emitted by the stimulable phosphor sheet. The cold mirror is a dichroic mirror having been set so as to transmit the stimulating rays and to reflect the light emitted by the stimulable phosphor sheet.
As the emitted light guiding means, the distributed index lens array, such as the SELFOC lens arrays or the rod lens array, constituted of an image forming system in which an object surface and an image surface correspond to each other in one-to-one relationship, the cylindrical lens, the slit, the optical fiber bundle, the hot mirror, the cold mirror, or the like, or a combination of two or more of the above-enumerated elements may be employed.
The stimulating ray cut-off filter (the sharp cut-off filter or the band-pass filter) for transmitting only the light emitted by the stimulable phosphor sheet and filtering out the stimulating rays should preferably be located in the optical path of the emitted light between the stimulable phosphor sheet and the line sensor and at a position that does not overlap the optical path of the stimulating rays. In this manner, the stimulating rays should preferably be prevented from impinging upon the line sensor.
The size of a light receiving surface of each of the photoelectric conversion device constituting the line sensor should preferably fall within the range of 10 xcexcm to 4,000 xcexcm, and should more preferably fall within the range of 100 xcexcm to 500 xcexcm. The number of the photoelectric conversion devices arrayed along the length direction of the line sensor should preferably be at least 1,000. The length of the line sensor should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet. The plurality of the photoelectric conversion devices may be arrayed in a straight line or in a zigzag pattern along the major axis direction.
In the third radiation image read-out method in accordance with the present invention, the line light source and the line sensor are located on the same surface side of the stimulable phosphor sheet.
The foregoing explanation of the third radiation image read-out method in accordance with the present invention also applies to a fourth radiation image read-out method in accordance with the present invention, which is described below.
As in the first radiation image read-out method in accordance with the present invention, the fourth radiation image read-out method in accordance with the present invention is characterized by utilizing a line sensor, which comprises a plurality of photoelectric conversion devices array along two-dimensional directions, in lieu of the line sensor employed in the third radiation image read-out method in accordance with the present invention, detecting light, which is emitted from a linear area of a stimulable phosphor sheet, with the line sensor, performing operation processing, such as addition, on outputs of the photoelectric conversion devices, which outputs have been obtained at respective scanning positions and correspond to an identical site on the stimulable phosphor sheet, and thereby enhancing a light collecting efficiency.
Specifically, in the fourth radiation image read-out method in accordance with the present invention, the first radiation image read-out method in accordance with the present invention is modified such that the linear stimulating rays are guided with stimulating ray guiding means to the area of the stimulable phosphor sheet, the light, which is emitted from the linear area of the stimulable phosphor sheet, is guided with emitted light guiding means to the line sensor, and at least part of an optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of an optical path of the emitted light from the stimulable phosphor sheet to the line sensor overlap each other.
The overlapping of at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light should preferably be achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other.
Fifth and sixth radiation image read-out methods in accordance with the present invention are characterized by utilizing a stimulable phosphor sheet having light emission region partitioned by a stimulating ray reflecting partition member into a plurality of fine cells.
Specifically, the present invention still further provides a fifth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of the linear area of the stimulable phosphor sheet, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet, and
iv) successively reading outputs of the line sensor in accordance with the movement,
wherein a light emission region of the stimulable phosphor sheet is partitioned by a stimulating ray reflecting partition member, which extends in a thickness direction of the stimulable phosphor sheet, into a plurality of fine cells.
In the fifth radiation image read-out method in accordance with the present invention, the size of the light receiving surface of each of the photoelectric conversion devices constituting the line sensor should preferably fall with the range of 10 xcexcm to 4,000 xcexcm, and should more preferably fall within the range of 100 xcexcm to 500 xcexcm. The number of the photoelectric conversion devices arrayed along the length direction of the line sensor should preferably be at least 1,000. The length of the line sensor should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet. The plurality of the photoelectric conversion devices may be arrayed in a straight line or in a zigzag pattern along the major axis direction.
The stimulable phosphor sheet employed in the fifth radiation image read-out method in accordance with the present invention comprises a substrate and a stimulable phosphor layer overlaid on the substrate. As will be described later with reference to FIG. 17A, the stimulable phosphor layer comprises a stimulable phosphor material, which emits light upon stimulation thereof, and the stimulating ray reflecting partition member, which partitions the stimulable phosphor material into a plurality of fine cells and suppresses scattering of the stimulating rays. As will be described later with reference to FIG. 17B, the stimulable phosphor material other than its front surface is surrounded by the stimulating ray reflecting partition member and the substrate. Alternatively, as will be described later with reference to FIG. 17C, the stimulable phosphor material other than its front surface is surrounded by only the stimulating ray reflecting partition member. The stimulable phosphor sheet may be produced by filling the stimulable phosphor material in the fine cells, which have been defined by only the stimulating ray reflecting partition member or by the stimulating ray reflecting partition member and the substrate.
Each of the stimulable phosphor material and the stimulating ray reflecting partition member should preferably be formed from a binder and a stimulable phosphor dispersed in the binder. The reflectivity of the stimulating ray reflecting partition member with respect to the stimulating rays should be higher than the reflectivity of the stimulable phosphor material with respect to the stimulating rays. For such purposes, by way of example, the binder-to-phosphor ratio (i.e., the B/P ratio) in the stimulable phosphor material may be set to be higher than the B/P ratio in the stimulating ray reflecting partition member. Alternatively, the particle size of the stimulable phosphor in the stimulable phosphor material may be set to be larger than the particle size of the stimulable phosphor in the stimulating ray reflecting partition member.
A coloring agent, such as an ultramarine, may be added to the stimulating ray reflecting partition member. Alternatively, as the stimulable phosphor contained in the stimulating ray reflecting partition member, a stimulable phosphor of a kind different from the stimulable phosphor contained in the stimulable phosphor material may be employed. For example, the stimulable phosphor contained in the stimulating ray reflecting partition member may be an ultraviolet light (UV light) emitting phosphor, which emits UV light capable of effecting primary stimulation of the stimulable phosphor. In cases where the stimulating ray reflecting partition member contains the coloring agent, the term xe2x80x9creflectivity of a stimulating ray reflecting partition member with respect to stimulating raysxe2x80x9d as used herein means the reflectivity of the stimulating ray reflecting partition member from which the coloring agent has been removed.
The size of each of the fine cells along the beam width direction should preferably be at most 1,000 xcexcm. The size of the each partition wall, which is formed by the stimulating ray reflecting partition member, along the beam width direction should preferably be at most 100 xcexcm. The thickness of the stimulable phosphor layer should preferably be at least 100 xcexcm.
Examples of such stimulable phosphor sheets include those described in Japanese Unexamined Patent Publication Nos. 59(1984)-202100, 62(1987)-36599, and 2(1990)-129600.
The term xe2x80x9clight emission region of a stimulable phosphor sheetxe2x80x9d as used herein means the region, which is filled with the stimulable phosphor material, in the aforesaid stimulable phosphor layer.
In the fifth radiation image read-out method in accordance with the present invention, the line light source and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. In cases where the line light source and the line sensor are located on opposite surface sides of the stimulable phosphor sheet, it is necessary to employ a stimulable phosphor sheet, wherein the stimulable phosphor material is surrounded by the stimulating ray reflecting partition member and a substrate formed from a material permeable to the emitted light, such that the emitted light may permeate to the surface side of the stimulable phosphor sheet opposite to the surface on the stimulating ray incidence side.
The foregoing explanation of the fifth radiation image read-out method in accordance with the present invention also applies to a sixth radiation image read-out method in accordance with the present invention, which is described below.
As in the first radiation image read-out method in accordance with the present invention, the sixth radiation image read-out method in accordance with the present invention is characterized by utilizing a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along two-dimensional directions, in lieu of the line sensor employed in the fifth radiation image read-out method in accordance with the present invention, detecting light, which is emitted from a linear area of a stimulable phosphor sheet, with the line sensor, performing operation processing, such as addition, on outputs of the photoelectric conversion devices, which outputs have been obtained at respective scanning positions and correspond to an identical site on the stimulable phosphor sheet, and thereby enhancing a light collecting efficiency.
Specifically, in the sixth radiation image read-out method in accordance with the present invention, the first radiation image read-out method in accordance with the present invention is modified such that a light emission region of the stimulable phosphor sheet is partitioned by a stimulating ray reflecting partition member, which extends in a thickness direction of the stimulable phosphor sheet, into a plurality of fine cells.
In the sixth radiation image read-out method in accordance with the present invention, as in the first radiation image read-out method in accordance with the present invention, the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction normal to the major axis direction, and the operation processing, such as addition, is performed on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet. Therefore in cases where the line width of the linear stimulating rays is larger than the width of each fine cell, the light simultaneously emitted from fine cells, which are adjacent to one another along the line width direction, is capable of being collected by corresponding rows of photoelectric conversion devices, and the light collecting efficiency can thereby be enhanced. Also, in cases where the width of each photoelectric conversion device is smaller than the width of each fine cell, the emitted light scattering to the line width direction in a single fine cell is capable of being collected by several corresponding rows of photoelectric conversion devices. As a result, the resolution and the light collecting efficiency can be enhanced.
Seventh, eighth, and ninth radiation image read-out methods in accordance with the present invention are characterized by utilizing a line light source and a line sensor, detecting image signals, which represent a radiation image having been stored on a stimulable phosphor sheet, from opposite surfaces of the stimulable phosphor sheet, and performing operation processing on the image signals.
Specifically, the present invention also provides a seventh radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed linearly, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement,
wherein the stimulable phosphor sheet is capable of emitting light from front and back surfaces,
two line sensors are utilized, each of which is located on one of the front and back surface sides of the stimulable phosphor sheet, the two line sensors detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
operation processing is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the seventh radiation image read-out method in accordance with the present invention, the LED array or the broad area laser should preferably be employed as the line light source. Also, the aforesaid stimulating ray guiding means should preferably be employed for suppressing spread of the stimulating rays to the direction (i.e., the minor axis direction), which is normal to the length direction (i.e., the major axis direction) of the line of the stimulating rays, such that the stimulating rays having been radiated out of the light source may take on the form of the linear stimulating rays on the surface of the stimulable phosphor sheet.
The stimulable phosphor sheet capable of emitting light from front and back surfaces, which is employed in the seventh radiation image read-out method in accordance with the present invention, is a stimulable phosphor sheet in which the substrate, or the like, is permeable to the emitted light, such that the emitted light caused to occur by the stimulating rays irradiated from at least one surface side of the stimulable phosphor sheet may emanate from the front and back surface of the stimulable phosphor sheet. In cases where two line light sources are located respectively on the front and back surface sides of the stimulable phosphor sheet, or in cases where the front and back surfaces of the stimulable phosphor sheet are stimulated one after another as in the eighth and ninth radiation image read-out methods in accordance with the present invention, which will be described later, it is necessary for the substrate of the stimulable phosphor sheet to be permeable to both the emitted light and the stimulating rays. Also, in cases where the front and back surfaces of the stimulable phosphor sheet are stimulated one after another, the stimulable phosphor sheet may be provided with a stimulating ray blocking layer as an intermediate layer.
Regardless of whether the stimulable phosphor sheet is stimulated from one surface side or is stimulated simultaneously or successively from the front and back surface sides, it is possible to employ a stimulable phosphor sheet, wherein the light emission region of the stimulable phosphor sheet is partitioned by a stimulating ray reflecting partition member, which extends in the thickness direction of the stimulable phosphor sheet, into a plurality of fine cells. Such a stimulable phosphor sheet is referred to as the anisotropic stimulable phosphor sheet. With the anisotropic stimulable phosphor sheet, the sharpness of an image reproduced from the image signal obtained from the photoelectric conversion can be enhanced.
In the seventh radiation image read-out method in accordance with the present invention, the plurality of the photoelectric conversion devices may be arrayed linearly in a straight line or in a zigzag pattern along the major axis direction. The size of a light receiving surface of each of the photoelectric conversion devices constituting the line sensor should preferably fall within the range of 10 xcexcm to 4,000 xcexcm, and should more preferably fall within the range of 100 xcexcm to 500 xcexcm. The number of the photoelectric conversion devices arrayed along the length direction of the line sensor should preferably be at least 1,000.
Also, the aforesaid emitted light guiding means may be located between the stimulable phosphor sheet and the line sensor.
The line sensor employed in the seventh radiation image read-out method in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the seventh radiation image read-out method in accordance with the present invention, simple addition, weighted addition, or one of other kinds of operation processing is performed on the image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet. Such processing is referred to as the superposition processing. The superposition processing is described in, for example, U.S. Pat. No. 4,356,398. With the superposition processing, noise occurring at random in the effective image storing region of the stimulable phosphor sheet can be reduced markedly, and slight differences in radiation absorptivity of an object can be illustrated clearly in an ultimately reproduced image, i.e., the detection capability can be enhanced markedly.
Unless otherwise specified, the foregoing explanation of the seventh radiation image read-out method in accordance with the present invention also applies to the eighth and ninth radiation image read-out methods in accordance with the present invention, which are described below.
As described above, in the seventh radiation image read-out method in accordance with the present invention, the two line sensors are located respectively on the opposite surface sides of the stimulable phosphor sheet. The eighth radiation image read-out method in accordance with the present invention is characterized by locating the line sensor on only one surface side of a stimulable phosphor sheet, shifting the line sensor to the opposite surface side of the stimulable phosphor sheet after an image signal has been detected from the one surface of the stimulable phosphor sheet, and thereby detecting an image signal from the opposite surface of the stimulable phosphor sheet.
Specifically, the present invention further provides an eighth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed linearly, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement,
wherein the stimulable phosphor sheet is capable of emitting light from front and back surfaces,
after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the line sensor is shifted by sensor shifting means to the opposite surface side of the stimulable phosphor sheet, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
operation processing is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the eighth radiation image read-out method in accordance with the present invention, the sensor shifting means may shift both the line sensor and the line light source to the opposite surface side of the stimulable phosphor sheet.
As described above, in the eighth radiation image read-out method in accordance with the present invention, the line sensor is shifted from one surface side to the opposite surface side of the stimulable phosphor sheet, and the image signal is thereby detected from the opposite surface side of the stimulable phosphor sheet. The ninth radiation image read-out method in accordance with the present invention is characterized by, instead of a line sensor being shifted, reversing front and back surfaces of a stimulable phosphor sheet, and thereby detecting an image signal from the opposite surface side of the stimulable phosphor sheet.
Specifically, the present invention still further provides a ninth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed linearly, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement,
wherein the stimulable phosphor sheet is capable of emitting light from front and back surfaces,
after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the front and back surfaces of the stimulable phosphor sheet are reversed by sheet reversing means, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
operation processing is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the seventh, eighth, and ninth radiation image read-out methods in accordance with the present invention, in cases where the line light source and the line sensor are located on the same surface side of the stimulable phosphor sheet, from the point of view of keeping the size of the radiation image read-out apparatus small, at least part of the optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of the optical path of the emitted light from the stimulable phosphor sheet to the line sensor should preferably overlap each other. Such a constitution is advantageous particularly in cases where two line sensors are located respectively on the opposite surface sides of the stimulable phosphor sheet (as in the seventh radiation image read-out method in accordance with the present invention). In cases where, besides the two line sensors, two line light sources are also located respectively on the opposite surface sides of the stimulable phosphor sheet, the effects of reducing the size of the radiation image read-out apparatus can be obtained by overlapping at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light at least on one surface side of the stimulable phosphor sheet. However, larger effects of reducing the size of the radiation image read-out apparatus can be obtained by partially overlapping the optical paths on the two surface sides of the stimulable phosphor sheet.
In cases where a single line sensor is utilized for detecting the images signals from the opposite surfaces of the stimulable phosphor sheet (as in the eighth and ninth radiation image read-out methods in accordance with the present invention), in the state in which the line sensor and the line light source are located on the same surface side of the stimulable phosphor sheet, the optical paths described above should preferably partially overlap each other. In this manner, the size of the radiation image read-out apparatus can be kept small.
Tenth, eleventh, and twelfth radiation image read-out methods in accordance with the present invention are characterized by utilizing a line light source and a line sensor, utilizing a stimulable phosphor sheet for energy subtraction processing, detecting image signals, which represent radiation images of a single object having been stored on the stimulable phosphor sheet, from opposite surfaces of the stimulable phosphor sheet, and performing a subtraction process on the image signals.
Specifically, the present invention also provides a tenth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed linearly, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement,
wherein the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information on one of the two radiation images, from a front surface, and emitting light, which carries information of the other radiation image, from a back surface,
two line sensors are utilized, each of which is located on one of the front and back surface sides of the stimulable phosphor sheet, the two line sensors detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
a subtraction process is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the tenth radiation image read-out method in accordance with the present invention, the LED array or the broad area laser should preferably be employed as the line light source. Also, the aforesaid stimulating ray guiding means should preferably be employed for suppressing spread of the stimulating rays to the direction (i.e., the minor axis direction), which is normal to the length direction (i.e., the major axis direction) of the line of the stimulating rays, such that the stimulating rays having been radiated out of the light source may take on the form of the linear stimulating rays on the surface of the stimulable phosphor sheet. Further, two light sources may be located on opposite surface sides of the stimulable phosphor sheet.
As the stimulable phosphor sheet for energy subtraction processing, a stimulable phosphor sheet having two stimulable phosphor layers formed at the front and back surfaces with a filter layer of a low radiation energy absorbing substance intervening therebetween may be employed. Alternatively, a stimulable phosphor sheet having two stimulable phosphor layers with different radiation energy absorption characteristics formed at the front and back surfaces may be employed. In cases where the front and back surfaces of the stimulable phosphor sheet are respectively stimulated (in cases where two line light sources are located respectively on the front and back surfaces of the stimulable phosphor sheet, or in cases where the front and back surfaces of the stimulable phosphor sheet are stimulated one after another, the stimulable phosphor sheet may be provided with a stimulating ray blocking layer as an intermediate layer.
Regardless of whether the stimulable phosphor sheet is stimulated from one surface side or is stimulated simultaneously from the front and back surface sides, it is possible to employ the anisotropic stimulable phosphor sheet described above. With the anisotropic stimulable phosphor sheet, the sharpness of an image reproduced from the image signal obtained from the photoelectric conversion can be enhanced.
In the tenth radiation image read-out method in accordance with the present invention, the plurality of the photoelectric conversion devices may be arrayed linearly in a straight line or in a zigzag pattern along the major axis direction. The size of a light receiving surface of each of the photoelectric conversion devices constituting the line sensor should preferably fall within the range of 10 xcexcm to 4,000 xcexcm, and should more preferably fall within the range of 100 xcexcm to 500 xcexcm. The number of the photoelectric conversion devices arrayed along the length direction of the line sensor should preferably be at least 1,000.
Also, the aforesaid emitted light guiding means may be located between the stimulable phosphor sheet and the line sensor.
The line sensor employed in the tenth radiation image read-out method in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the tenth radiation image read-out method in accordance with the present invention, the subtraction process is performed on the image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet. Specifically, the image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet, may be subtracted from each other with Formula (1) shown below. For such purposes, a combination of a flame memory and a subtracter, or the like, may be employed.
Sproc=Ka.SHxe2x88x92Kb.SL+Kc xe2x80x83xe2x80x83(1) 
in which Sproc represents the subtraction image signal obtained from the subtractions process, each of Ka and Kb represents the weight factor, and Kc represents the bias component (Ka, Kb, and Kc will hereinbelow be referred to as the parameters for the subtraction process), SH represents the high energy image signal representing the radiation image formed with radiation having a high energy level, and SL represents the low energy image signal representing the radiation image formed with radiation having a low energy level.
Unless otherwise specified, the foregoing explanation of the tenth radiation image read-out method in accordance with the present invention also applies to the eleventh and twelfth radiation image read-out methods in accordance with the present invention, which are described below.
As described above, in the tenth radiation image read-out method in accordance with the present invention, the two line sensors are located respectively on the opposite surface sides of the stimulable phosphor sheet. The eleventh radiation image read-out method in accordance with the present invention is characterized by locating the line sensor on only one surface side of a stimulable phosphor sheet, shifting the line sensor to the opposite surface side of the stimulable phosphor sheet after an image signal has been detected from the one surface of the stimulable phosphor sheet, and thereby detecting an image signal from the opposite surface of the stimulable phosphor sheet.
Specifically, the present invention further provides an eleventh radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed linearly, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement,
wherein the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information of one of the two radiation images, from a front surface, and emitting light, which carries information of the other radiation image, from a back surface,
after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the line sensor is shifted by sensor shifting means to the opposite surface side of the stimulable phosphor sheet, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
a subtraction process is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the eleventh radiation image read-out method in accordance with the present invention, the sensor shifting means may shift both the line sensor and the line light source to the opposite surface side of the stimulable phosphor sheet.
As described above, in the eleventh radiation image read-out method in accordance with the present invention, the line sensor is shifted from one surface side to the opposite surface side of the stimulable phosphor sheet, and the image signal is thereby detected from the opposite surface side of the stimulable phosphor sheet. The twelfth radiation image read-out method in accordance with the present invention is characterized by, instead of a line sensor being shifted, reversing front and back surfaces of a stimulable phosphor sheet, and thereby detecting an image signal from the opposite surface side of the stimulable phosphor sheet.
Specifically, the present invention still further provides a twelfth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed linearly, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement,
wherein the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information of one of the two radiation images, from a front surface, and emitting light, which carries information of the other radiation image, from a back surface,
after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the front and back surfaces of the stimulable phosphor sheet are reversed by sheet reversing means, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
a subtraction process is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the tenth, eleventh, and twelfth radiation image read-out methods in accordance with the present invention, in cases where the line light source and the line sensor are located on the same surface side of the stimulable phosphor sheet, from the point of view of keeping the size of the radiation image read-out apparatus small, at least part of the optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of the optical path of the emitted light from the stimulable phosphor sheet to the line sensor should preferably overlap each other. Such a constitution is advantageous particularly in cases where two line sensors are located respectively on the opposite surface sides of the stimulable phosphor sheet (as in the tenth radiation image read-out method in accordance with the present invention). In cases where, besides the two line sensors, two line light sources are also located respectively on the opposite surface sides of the stimulable phosphor sheet, the effects of reducing the size of the radiation image read-out apparatus can be obtained by overlapping at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light at least on one surface side of the stimulable phosphor sheet. However, larger effects of reducing the size of the radiation image read-out apparatus can be obtained by partially overlapping the optical paths on the two surface sides of the stimulable phosphor sheet.
In cases where a single line sensor is utilized for detecting the images signals from the opposite surfaces of the stimulable phosphor sheet (as in the eleventh and twelfth radiation image read-out methods in accordance with the present invention), in the state in which the line sensor and the line light source are located on the same surface side of the stimulable phosphor sheet, the optical paths described above should preferably partially overlap each other. In this manner, the size of the radiation image read-out apparatus can be kept small.
Thirteenth and fourteenth radiation image read-out methods in accordance with the present invention are characterized by reading out a radiation image, which has been stored on a stimulable phosphor sheet, by utilizing a back illuminated type of CCD image sensor.
Specifically, the present invention also provides a thirteenth radiation image read-out method, comprising the steps of:
i) irradiating stimulating rays, which have been produced by a surface light source, onto a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the area of the front surface of the stimulable phosphor sheet exposed to the stimulating rays or from an area of a back surface of the stimulable phosphor sheet corresponding to the area of the front surface of the stimulable phosphor sheet, with an area sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by the area sensor, and
iii) reading outputs of the photoelectric conversion devices constituting the area sensor,
wherein the area sensor is a back illuminated type of CCD image sensor.
The present invention further provides a fourteenth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and
iv) successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,
wherein the line sensor is a back illuminated type of CCD image sensor.
In the fourteenth radiation image read-out method in accordance with the present invention, as in the first radiation image read-out method in accordance with the present invention, the back illuminated type of CCD image sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear area of the stimulable phosphor sheet and the direction, which is normal to the length direction.
In the thirteenth and fourteenth radiation image read-out methods in accordance with the present invention, the back illuminated type of CCD image sensor should preferably be cooled with cooling means.
An ordinarily utilized front illuminated type of CCD image sensor detects light incident from the front surface. The back illuminated type of CCD image sensor detects light incident from the back surface. For such purposes, for example, the back surface of the back illuminated type of CCD image sensor is scraped.
The front illuminated type of CCD image sensor is provided with a protective layer constituted of Si, or the like, and therefore the sensitivity of the front illuminated type of CCD image sensor with respect to light of a short wavelength region, such as blue light, is markedly low. The back illuminated type of CCD image sensor has markedly high sensitivity with respect to light falling within the range of an ultraviolet region to a blue light region. Also, the back illuminated type of CCD image sensor has a high quantum efficiency, and its sensitivity with respect to light falling within the range of a visible light region to an infrared region is higher than that of the front illuminated type of CCD image sensor.
As the cooling means for cooling the back illuminated type of CCD image sensor, means utilizing a Peltier device, or the like, may be employed.
The back illuminated type of CCD image sensor should preferably be produced by arraying a plurality of back illuminated type of CCD image sensors chips. For example, in cases where the back illuminated type of CCD image sensor is employed as the line sensor, the back illuminated type of CCD image sensor may comprise a plurality of back illuminated type of CCD image sensor chips arrayed in a straight line of in a zigzag pattern along the length direction of the linear area of the stimulable phosphor sheet. Each of the back illuminated type of CCD image sensor chips may comprise a plurality of photoelectric conversion devices arrayed in two-dimensional directions an in a matrix-like pattern or in a zigzag pattern.
In the thirteenth and fourteenth radiation image read-out methods in accordance with the present invention, as the light source, an LED array, an organic EL device, a fluorescent lamp, a high-pressure sodium lamp, a cold cathode tube, or the like, may be employed. The light source is not limited to a light source having a surface-like shape or a linear shape and may be one of various other light sources, which irradiate linear or surface-like (area-like) stimulating rays onto the surface of the stimulable phosphor sheet. Alternatively, the light source may be provided with an expanding mechanism for expanding the radiated stimulating rays such that linear or surface-like stimulating rays may impinge upon the surface of the stimulable phosphor sheet. In cases where the light source is the line light source, the broad area laser, or the like, which radiates linear stimulating rays, may be employed as the light source.
The stimulating rays may be radiated continuously out of the light source or may be pulsed stimulating rays radiated intermittently out of the light source. From the point of view of reducing noise, the stimulating rays should preferably be pulsed stimulating rays having high intensity. Also, the stimulating rays should have wavelengths falling within the stimulation wavelength range for the stimulable phosphor sheet. For example, in cases where the stimulable phosphor sheet is capable of being stimulated by red stimulating rays, the stimulating rays should have wavelengths falling within the range of 600 nm to 1,000 nm, and should preferably have wavelengths falling within the range of 600 nm to 700 nm.
The line sensor employed in the fourteenth radiation image read-out method in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the fourteenth radiation image read-out method in accordance with the present invention, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the operation processing may be performed on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet.
In the thirteenth radiation image read-out method in accordance with the present invention, the light source and the area sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. Also, in the fourteenth radiation image read-out method in accordance with the present invention, the line light source and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet.
In the thirteenth and fourteenth radiation image read-out methods in accordance with the present invention, the stimulating rays irradiated to the stimulable phosphor sheet should preferably be set such that the power (correspond to the irradiation intensity or the luminance) of the stimulating rays may not vary. In cases where variation in power of the stimulating rays occur, the intensity of the stimulating rays may be monitored with a monitoring means. When variation in power occurs, for example, the driving voltage for the light source (or the line light source), or the like, may be modulated with modulating means more quickly than the photoelectric conversion speed of the photoelectric conversion devices such that the emission power (the luminance) of the light source (or the line light source) may become equal to a predetermined value. In this manner, adverse effects of power variation may be suppressed.
Fifteenth and sixteenth radiation image read-out methods in accordance with the present invention are characterized by reading out a radiation image, which has been stored on a stimulable phosphor sheet, by utilizing a stimulating ray source constituted of an organic EL device.
Specifically, the present invention still further provides a fifteenth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by the line sensor,
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and
iv) successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,
wherein the line light source is constituted of an organic EL device.
The present invention also provides a sixteenth radiation image read-out method, comprising the steps of:
i) irradiating stimulating rays, which have been produced by a surface light source, onto a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the area of the front surface of the stimulable phosphor sheet exposed to the stimulating rays or from an area of a back surface of the stimulable phosphor sheet corresponding to the area of the front surface of the stimulable phosphor sheet, with an area sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by the area sensor, and
iii) reading outputs of the photoelectric conversion devices constituting the area sensor,
wherein the surface light source is constituted of an organic EL device.
The organic EL device (also referred to as the organic LED) is an electric current injection type of luminous device, in which the energy of recombination of positive holes and electrons injected into an organic material is converted into optical energy and light emission is thereby effected. The organic EL device is a self-luminous device capable of emanating strong light having luminous intensity of several hundreds of thousands of candelas (i.e., capable of emitting light with high luminance) (the luminance of an ordinary white fluorescent lamp is 1,000 to 5,000 candelas), and having an energy conversion efficiency of at least 101 m/W (i.e., having a high luminous efficiency). The organic EL device has various characteristic properties such as that it can be driven with a low d.c. voltage of at most 10 V, can respond quickly on the nS order, can emit light of various colors ranging from blue to red, does not have dependence upon field angle as in liquid crystal devices, and is very thin and light in weight. By virtue of the characteristic properties, the organic EL device has recently attracted particular attention and has been used in practice. The organic EL device employed in the fifteenth and sixteenth radiation image read-out methods in accordance with the present invention may be of one of various materials and one of various structures and may be produced by one of various production processes.
In the fifteenth and sixteenth radiation image read-out methods in accordance with the present invention, the light source constituted of the organic EL device is not limited to those which produce the surface-like or line-like stimulating rays, and may be one of various other light sources, which irradiate linear or surface-like (area-like) stimulating rays onto the surface of the stimulable phosphor sheet. Alternatively, the light source may be provided with an expanding mechanism for expanding the radiated stimulating rays such that linear or surface-like stimulating rays may impinge upon the surface of the stimulable phosphor sheet.
The stimulating rays may be radiated continuously out of the organic EL device or may be pulsed stimulating rays radiated intermittently out of the organic EL device. From the point of view of reducing noise, the stimulating rays should preferably be pulsed stimulating rays having high intensity. Also, the stimulating rays produced by the organic EL device should have wavelengths falling within the stimulation wavelength range for the stimulable phosphor sheet. For example, in cases where the stimulable phosphor sheet is capable of being stimulated by red stimulating rays, the stimulating rays should have wavelengths falling within the range of 600 nm to 1,000 nm, and should preferably have wavelengths falling within the range of 600 nm to 700 nm.
The line sensor employed in the fifteenth radiation image read-out method in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the fifteenth radiation image read-out method in accordance with the present invention, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the operation processing may be performed on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet.
In the fifteenth radiation image read-out method in accordance with the present invention, the organic EL device and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. Also, in the sixteenth radiation image read-out method in accordance with the present invention, the organic EL device and the area sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet.
In the fifteenth and sixteenth radiation image read-out methods in accordance with the present invention, the stimulating rays irradiated to the stimulable phosphor sheet should preferably be set such that the power (corresponding to the irradiation intensity or the luminance) of the stimulating rays may not vary. In cases where variation in power of the stimulating rays occur, the intensity of the stimulating rays may be monitored with a monitoring means. When variation in power occurs, the driving voltage for the organic EL device may be modulated with modulating means more quickly than the photoelectric conversion speed of the photoelectric conversion devices such that the emission power (the luminance) of the organic EL device may become equal to a predetermined value. In this manner, adverse effects of power variation may be suppressed.
The present invention further provides a seventeenth radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) guiding light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with light guiding optical system to a line sensor comprising a plurality of arrayed photoelectric conversion devices,
iii) receiving the emitted light with the line sensor, the received light being subjected to photoelectric conversion performed by the line sensor, and
iv) moving the stimulable phosphor sheet with respect to the line light source the light guiding optical system, and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet,
wherein the light guiding optical system has been subjected to coloring for transmitting only the emitted light and filtering out the stimulating rays.
The present invention also provides a first radiation image read-out apparatus for carrying out the first radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a first radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed along each of a length direction of the linear area of the stimulable phosphor sheet and a direction normal to the length direction,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet, and
iv) reading means for successively reading outputs of the line sensor in accordance with the movement, the reading means being provided with operation means for performing operation processing on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement performed by the scanning means and correspond to an identical site on the stimulable phosphor sheet.
In the first radiation image read-out apparatus in accordance with the present invention, as the line sensor, an amorphous silicon sensor, a CCD image sensor, a CCD image sensor with back illuminator, a MOS image sensor, or the like, may be employed. The line sensor may comprise a plurality of sensor chips (CCD image sensor chips, MOS image sensor chips, or the like) arrayed in a straight line or in a zigzag pattern along the length direction of the linear area of the stimulable phosphor sheet. Each of the sensor chips may comprise a plurality of photoelectric conversion devices arrayed in two-dimensional directions and in a matrix-like pattern or in a zigzag pattern.
The present invention further provides a second radiation image read-out apparatus for carrying out the second radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides a second radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of arrayed photoelectric conversion devices,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and
iv) reading means for successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,
wherein the line light source is a broad area laser, which linearly radiates out the stimulating rays.
The line sensor employed in the second radiation image read-out apparatus in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the second radiation image read-out apparatus in accordance with the present invention, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the reading means may be provided with the operation means for performing the operation processing on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement performed by the scanning means and correspond to an identical site on the stimulable phosphor sheet. In such cases, if the beam width of the light emitted by the stimulable phosphor sheet is larger than the width of each photoelectric conversion device, the line sensor as a whole can receive the emitted light over approximately the entire beam width. The operation means provided in the reading means performs the operation processing, such as addition processing, on the outputs of the photoelectric conversion devices, which outputs correspond to an identical site on the stimulable phosphor sheet. In this manner, the light receiving efficiency can be enhanced.
The present invention still further provides a third radiation image read-out apparatus for carrying out the third radiation image read-out method in accordance with the present invention. Specifically, the present invention still further provides a third radiation image read-out apparatus, comprising:
i) a line light source for linearly radiating stimulating rays, which have been produced by a line light source,
ii) stimulating rays guiding means for guiding the linear stimulating rays to an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
iii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of the linear area of the stimulable phosphor sheet,
iv) emitted light guiding means for guiding the light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, to the line sensor,
v) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet, and
vi) reading means for successively reading outputs of the line sensor in accordance with the movement,
wherein at least part of an optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of an optical path of the emitted light from the stimulable phosphor sheet to the line sensor overlap each other.
In the third radiation image read-out apparatus in accordance with the present invention, the overlapping of at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light should preferably be achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other.
The present invention also provides a fourth radiation image read-out apparatus for carrying out the fourth radiation image read-out method in accordance with the present invention. In the fourth radiation image read-out apparatus in accordance with the present invention, the first radiation image read-out apparatus in accordance with the present invention is modified such that the apparatus further comprises stimulating ray guiding means for guiding the linear stimulating rays to the area of the stimulable phosphor sheet, and emitted light guiding means for guiding the light, which is emitted from the linear area of the stimulable phosphor sheet, to the line sensor, and at least part of an optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of an optical path of the emitted light from the stimulable phosphor sheet to the line sensor overlap each other.
In the fourth radiation image read-out apparatus in accordance with the present invention, the overlapping of at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light should preferably be achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other.
The present invention further provides a fifth radiation image read-out apparatus for carrying out the fifth radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides a fifth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of the linear area of the stimulable phosphor sheet,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet, and
iv) reading means for successively reading outputs of the line sensor in accordance with the movement,
wherein a light emission region of the stimulable phosphor sheet is partitioned by a stimulating ray reflecting partition member, which extends in a thickness direction of the stimulable phosphor sheet, into a plurality of fine cells.
The present invention still further provides a sixth radiation image read-out apparatus for carrying out the six radiation image read-out method in accordance with the present invention. In the sixth radiation image read-out apparatus in accordance with the present invention, the first radiation image read-out apparatus in accordance with the present invention is modified such that a light emission region of the stimulable phosphor sheet is partitioned by a stimulating ray reflecting partition member, which extends in a thickness direction of the stimulable phosphor sheet, into a plurality of fine cells.
The present invention also provides a seventh radiation image read-out apparatus for carrying out the seventh radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a seventh radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed linearly,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading means for reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement performed by the scanning means,
wherein the stimulable phosphor sheet is capable of emitting light from front and back surfaces,
two line sensors are utilized, each of which is located on one of the front and back surface sides of the stimulable phosphor sheet, the two line sensors detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
the reading means performs operation processing on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the seventh radiation image read-out apparatus in accordance with the present invention (and in eighth and ninth radiation image read-out apparatuses in accordance with the present invention, which will be described later), the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
The present invention further provides an eighth radiation image read-out apparatus for carrying out the eighth radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides an eighth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed linearly,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading means for reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement performed by the scanning means,
wherein the stimulable phosphor sheet is capable of emitting light from front and back surfaces,
the apparatus further comprises sensor shifting means for operating such that, after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the sensor shifting means shifts the line sensor to the opposite surface side of the stimulable phosphor sheet, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
the reading means performs operation processing on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the eighth radiation image read-out apparatus in accordance with the present invention, the sensor shifting means may shift both the line sensor and the line light source to the opposite surface side of the stimulable phosphor sheet.
The present invention still further provides a ninth radiation image read-out apparatus for carrying out the ninth radiation image read-out method in accordance with the present invention. Specifically, the present invention still further provides a ninth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed linearly,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading means for reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement performed by the scanning means,
wherein the stimulable phosphor sheet is capable of emitting light from front and back surfaces,
the apparatus further comprises sheet reversing means for operating such that, after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the sheet reversing means reverses the front and back surfaces of the stimulable phosphor sheet, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
the reading means performs operation processing on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the seventh, eighth, and ninth radiation image read-out apparatuses in accordance with the present invention, in cases where the line light source and the line sensor are located on the same surface side of the stimulable phosphor sheet, from the point of view of keeping the size of the radiation image read-out apparatus small, at least part of the optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of the optical path of the emitted light from the stimulable phosphor sheet to the line sensor should preferably overlap each other.
The present invention also provides a tenth radiation image read-out apparatus for carrying out the tenth radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a tenth radiation image read-out apparatus, comprising:
i) i) a line light source for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed linearly,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading means for reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement performed by the scanning means,
wherein the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information of one of the two radiation images, from a front surface, and emitting light, which carries information of the other radiation image, from a back surface,
two line sensors are utilized, each of which is located on one of the front and back surface sides of the stimulable phosphor sheet, the two line sensors detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
the reading means is provided with means for performing a subtraction process on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the tenth radiation image read-out apparatus in accordance with the present invention (and in eleventh and twelfth radiation image read-out apparatuses in accordance with the present invention, which will be described later), the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
The present invention further provides an eleventh radiation image read-out apparatus for carrying out the eleventh radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides an eleventh radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed linearly,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading means for reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement performed by the scanning means,
wherein the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information of one of the two radiation images, from a front surface, and emitting light, which carries information of the other radiation image, from a back surface,
the apparatus further comprises sensor shifting means for operating such that, after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the sensor shifting means shifts the line sensor to the opposite surface side of the stimulable phosphor sheet, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
the reading means is provided with means for performing a subtraction process on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the eleventh radiation image read-out apparatus in accordance with the present invention, the sensor shifting means may shift both the line sensor and the line light source to the opposite surface side of the stimulable phosphor sheet.
The present invention still further provides a twelfth radiation image read-out apparatus for carrying out the twelfth radiation image read-out method in accordance with the present invention. Specifically, the present invention still further provides a twelfth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of photoelectric conversion devices arrayed linearly,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor, and
iv) reading means for reading outputs of the photoelectric conversion devices constituting the line sensor, which outputs are obtained at respective positions of movement performed by the scanning means,
wherein the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information of one of the two radiation images, from a front surface, and emitting light, which carries information of the other radiation image, from a back surface,
the apparatus further comprises sensor sheet reversing means for operating such that, after detection of the emitted light from one of the front and back surfaces of the stimulable phosphor sheet has been finished, the sheet reversing means reverses the front and back surfaces of the stimulable phosphor sheet, the line sensor thereby detecting two image signals, each of which is made up of a series of image signal components representing pixels in the radiation image, from the front and back surfaces of the stimulable phosphor sheet, and
the reading means is provided with means for performing a subtraction process on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet.
In the tenth, eleventh, and twelfth radiation image read-out apparatuses in accordance with the present invention, in cases where the line light source and the line sensor are located on the same surface side of the stimulable phosphor sheet, from the point of view of keeping the size of the radiation image read-out apparatus small, at least part of the optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of the optical path of the emitted light from the stimulable phosphor sheet to the line sensor should preferably overlap each other.
The present invention also provides a thirteenth radiation image read-out apparatus for carrying out the thirteenth radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a thirteenth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) an area sensor for receiving light, which is emitted from the area of the front surface of the stimulable phosphor sheet exposed to the stimulating rays or from an area of a back surface of the stimulable phosphor sheet corresponding to the area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the area sensor comprising a plurality of arrayed photoelectric conversion devices, and
iii) reading means for reading outputs of the photoelectric conversion devices constituting the area sensor,
wherein the area sensor is a back illuminated type of CCD image sensor.
The present invention further provides a fourteenth radiation image read-out apparatus for carrying out the fourteenth image read-out method in accordance with the present invention. Specifically, the present invention further provides a fourteenth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of arrayed photoelectric conversion devices,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and
iv) reading means for successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,
wherein the line sensor is a back illuminated type of CCD image sensor.
In the fourteenth radiation image read-out apparatus in accordance with the present invention, as in the first radiation image read-out apparatus in accordance with the present invention, the back illuminated type of CCD image sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear area of the stimulable phosphor sheet and the direction, which is normal to the length direction.
The thirteenth and fourteenth radiation image read-out apparatuses in accordance with the present invention should preferably further comprise cooling means for cooling the back illuminated type of CCD image sensor.
As the cooling means for cooling the back illuminated type of CCD image sensor, means utilizing a Peltier device, or the like, may be employed.
The back illuminated type of CCD image sensor should preferably be produced by arraying a plurality of back illuminated type of CCD image sensor chips. For example, in cases where the back illuminated type of CCD image sensor is employed as the line sensor, the back illuminated type of CCD image sensor may comprise a plurality of back illuminated type of CCD image sensor chips arrayed in a straight line or in a zigzag pattern along the length direction of the linear area of the stimulable phosphor sheet. Each of the back illuminated type of CCD image sensor chips may comprise a plurality of photoelectric conversion devices arrayed in two-dimensional directions and in a matrix-like pattern or in a zigzag pattern.
The line sensor employed in the fourteenth radiation image read-out apparatus in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the fourteenth radiation image read-out apparatus in accordance with the present invention, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the reading means may be provided with operation means for performing operation processing on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement performed by the scanning means and correspond to an identical site on the stimulable phosphor sheet.
The present invention still further provides a fifteenth radiation image read-out apparatus for carrying out the fifteenth radiation image read-out method in accordance with the present invention. Specifically, the present invention still further provides a fifteenth radiation image read-out apparatus, comprising:
i) a line light source for linearly irradiating stimulating rays onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of arrayed photoelectric conversion devices,
iii) scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and
iv) reading means for successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,
wherein the line light source is constituted of an organic EL device.
The present invention also provides a sixteenth radiation image read-out apparatus for carrying out the sixteenth radiation image read-out method in accordance with the present invention. Specifically, the present invention also provides a sixteenth radiation image read-out apparatus, comprising:
i) a surface light source for irradiating stimulating rays onto a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) an area sensor for receiving light, which is emitted from the area of the front surface of the stimulable phosphor sheet exposed to the stimulating rays or from an area of a back surface of the stimulable phosphor sheet corresponding to the area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the area sensor comprising a plurality of arrayed photoelectric conversion devices, and
iii) reading means for reading outputs of the photoelectric conversion devices constituting the area sensor,
wherein the surface light source is constituted of an organic EL device.
The line sensor employed in the fifteenth radiation image read-out apparatus in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.
In the fifteenth radiation image read-out apparatus in accordance with the present invention, as in the first radiation image read-out apparatus in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the reading means may be provided with operation means for performing operation processing on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement performed by the scanning means and correspond to an identical site on the stimulable phosphor sheet.
The present invention further provides a seventeenth radiation image read-out apparatus for carrying out the seventeenth radiation image read-out method in accordance with the present invention. Specifically, the present invention further provides a seventeenth radiation image read-out apparatus, comprising:
i) line light source for linearly irradiating stimulating rays onto an area of a front surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, and performing photoelectric conversion of the received light, the line sensor comprising a plurality of arrayed photoelectric conversion devices,
iii) a light guiding optical system for guiding the emitted light, the light guiding optical system being located between the stimulable phosphor sheet and the line sensor, and
iv) scanning means for moving the stimulable phosphor sheet with respect to the line light source, the light guiding optical system, and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet,
wherein the light guiding optical system has been subjected to coloring for transmitting only the emitted light and filtering out the stimulating rays.
With the first radiation image read-out method and apparatus in accordance with the present invention, the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear light emitted by the stimulable phosphor sheet and the direction normal to the length direction. Therefore, if the light receiving width of each photoelectric conversion device is smaller than the line width of the light emitted by the stimulable phosphor sheet (i.e., the line width on the light receiving surface of the photoelectric conversion device), the line sensor as a whole can receive the emitted light over approximately the entire line width of the emitted light. As a result, the light receiving efficiency can be enhanced. Also, the operation means performs the operation processing, such as addition processing, on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement of the stimulable phosphor sheet or the line sensor performed by the scanning means and which correspond to an identical site on the stimulable phosphor sheet. In this manner, the light collecting efficiency at each site on the stimulable phosphor sheet can be enhanced. Further, since the light receiving width of each photoelectric conversion device is not set to be large for an increase in the light receiving size, the resolution does not become low, and a desired level of resolution can be obtained.
Furthermore, in cases where the line sensor is produced by arraying a plurality of sensor chips, it can be produced with a simple production process, the yield of the products in the production process can be enhanced, and the cost can be kept low. Particularly, in cases where the sensor chips are arrayed in a zigzag pattern, free regions which are not occupied by sensor chips can be formed in the line sensor, and electric circuits for pixel shift compensation and other elements can be located at the free regions.
In the first radiation image read-out method and apparatus (and the second to twelfth radiation image read-out methods and apparatuses) in accordance with the present invention, the line sensor is employed as the photoelectric read-out means. Therefore, the advantages over conventional radiation image read-out methods and apparatuses utilizing photoelectric read-out means other than the line sensor can be obtained in that the time required to detect the emitted light can be kept short, the apparatus size can be reduced, and the cost can be kept low due to reduction in mechanical scanning optical parts, and the like.
With the second radiation image read-out method and apparatus in accordance with the present invention, the linear laser beam, which is coherent light, is irradiated from the broad area laser to the stimulable phosphor sheet, and the radiation image stored on the stimulable phosphor sheet is thereby read out. Therefore, the second radiation image read-out method and apparatus in accordance with the present invention are advantageous over radiation image read-out methods and apparatuses utilizing a fluorescent lamp, a cold cathode fluorescent lamp, or an LED array as the light source in that the directivity of the stimulating rays is high, the intensity of the stimulating rays is high, and therefore high stimulation energy can be imparted to the stimulable phosphor sheet. As a result, an image having a high signal-to-noise ratio can be obtained.
With the second radiation image read-out method and apparatus in accordance with the present invention, wherein the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear light emitted by the stimulable phosphor sheet and the direction normal to the length direction, the same effects as those with the first radiation image read-out method and apparatus in accordance with the present invention can be obtained.
With the third and fourth radiation image read-out methods and apparatuses in accordance with the present invention, wherein at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light overlap each other, the space occupied by the optical paths can be reduced, and the size of the entire radiation image read-out apparatus can be reduced. In cases where the overlapping of the optical paths is achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other, at least part of the optical elements of the stimulating ray guiding means and the emitted light guiding means can be omitted. Therefore, the cost can be kept low.
With the fourth radiation image read-out method and apparatus in accordance with the present invention, wherein the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear light emitted by the stimulable phosphor sheet and the direction normal to the length direction, the same effects as those with the first radiation image read-out method and apparatus in accordance with the present invention can be obtained.
With the fifth and sixth radiation image read-out methods and apparatuses in accordance with the present invention, wherein the light emission region of the stimulable phosphor sheet is partitioned by the stimulating ray reflecting partition member into a plurality of fine cells, the stimulating rays impinging upon the predetermined area (the linear area) of the stimulable phosphor sheet can be prevented from scattering boundlessly beyond the fine cells in the stimulable phosphor sheet. Therefore, the light is emitted from only the line width area approximately identical with the linear area upon which the stimulating rays impinge. Accordingly, the light collecting efficiency of the line sensor can be enhanced without the desired resolution becoming low.
Also, the emitted light occurs in units of fine cells, and therefore the sharpness of the image reproduced from an image signal having been obtained from the photoelectric conversion can be enhanced.
With the sixth radiation image read-out method and apparatus in accordance with the present invention, as in the first radiation image read-out method and apparatus in accordance with the present invention, the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear light emitted by the stimulable phosphor sheet and the direction normal to the length direction, and the operation processing is performed on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet. Therefore, in cases where the line width of the linear stimulating rays is larger than the width of each fine cell, the light simultaneously emitted from fine cells, which are adjacent to one another along the line width direction, is capable of being collected by corresponding rows of photoelectric conversion devices, and the light collecting efficiency can be enhanced by, for example, adding outputs of the photoelectric conversion devices. Also, in cases where the width of each photoelectric conversion device is smaller than the width of each fine cell, the emitted light scattering to the line width direction in a single fine cell is capable of being collected by several corresponding rows of photoelectric conversion devices. As a result, the resolution and the light collecting efficiency can be enhanced.
With the seventh, eighth, and ninth radiation image read-out methods and apparatuses in accordance with the present invention, image signals representing the radiation image having been stored on the stimulable phosphor sheet are detected from the front and back surfaces of the stimulable phosphor sheet, and the operation processing is performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet. Therefore, noise occurring at random in the effective image storing region of the stimulable phosphor sheet can be reduced markedly, and slight differences in radiation absorptivity of an object can be illustrated clearly in the ultimately reproduced image, i.e., the detection capability can be enhanced markedly.
Also, with the seventh, eighth, and ninth radiation image read-out methods and apparatuses in accordance with the present invention, wherein the line sensor comprises a plurality of rows of photoelectric conversion devices as in the first radiation image read-out method and apparatus in accordance with the present invention, if the light receiving width of each photoelectric conversion device (i.e., the width taken along the minor axis direction of the line sensor) is smaller than the line width of the light emitted by the stimulable phosphor sheet, the line sensor as a whole can receive the emitted light over approximately the entire line width of the emitted light. As a result, the light receiving efficiency can be enhanced.
With the tenth, eleventh, and twelfth radiation image read-out methods and apparatuses in accordance with the present invention, the stimulable phosphor sheet is a stimulable phosphor sheet for energy subtraction processing, which stores two radiation images of a single object formed with radiation having different energy distributions, the stimulable phosphor sheet being capable of emitting light, which carries information of one of the two radiation images, from the front surface, and emitting light, which carries information of the other radiation image, from the back surface. Two image signals are detected from the front and back surfaces of the stimulable phosphor sheet by utilizing the line sensor. The subtraction process is then performed on image signal components of the two image signals, which image signal components represent corresponding pixels on the front and back surfaces of the stimulable phosphor sheet. In this manner, a subtraction image, in which only the pattern of a specific tissue or structure embedded in the radiation image has been enhanced or extracted, can be obtained easily.
Also, with the tenth, eleventh, and twelfth radiation image read-out methods and apparatuses in accordance with the present invention, wherein the line sensor comprises a plurality of rows of photoelectric conversion devices as in the first radiation image read-out method and apparatus in accordance with the present invention, if the light receiving width of each photoelectric conversion device (i.e., the width taken along the minor axis direction of the line sensor) is smaller than the line width of the light emitted by the stimulable phosphor sheet, the line sensor as a whole can receive the emitted light over approximately the entire line width of the emitted light. As a result, the light receiving efficiency can be enhanced.
With the thirteenth and fourteenth radiation image read-out methods and apparatuses in accordance with the present invention, the radiation image having been stored on the stimulable phosphor sheet is read out by utilizing the back illuminated type of CCD image sensor having a high quantum efficiency. Therefore, it is possible to obtain an image signal having a higher level than with the ordinarily utilized front illuminated type of CCD image sensor. As a result, an image having good image quality with a high signal-to-noise ratio can be obtained. Also, the back illuminated type of CCD image sensor can perform light detection more quickly and more accurately than the front illuminated type of CCD image sensor, and therefore quick and accurate light detection as with a photomultiplier can be achieved.
The quantum efficiency of the back illuminated type of CCD image sensor is high over the ultraviolet to infrared region. Particularly, the back illuminated type of CCD image sensor has the characteristic features in that, in the ultraviolet to blue region, the quantum efficiency is markedly high (e.g., at least 50%). (In the ultraviolet to blue region, the quantum efficiency of the front illuminated type of CCD image sensor is approximately zero.) In cases where the back illuminated type of CCD image sensor is utilized in combination with, particularly, a stimulable phosphor sheet emitting blue light, the emitted light utilization efficiency can be enhanced markedly, and markedly large effects of obtaining images having good quality can be obtained.
In cases where the cooling means for cooling the back illuminated type of CCD image sensor is utilized, the dark output can be reduced, and an image having good image quality free from noise can be obtained.
With the fourteenth radiation image read-out method and apparatus in accordance with the present invention, wherein the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear light emitted by the stimulable phosphor sheet and the direction normal to the length direction, the same effects as those with the first radiation image read-out method and apparatus in accordance with the present invention can be obtained.
Further, in cases where the back illuminated type of CCD image sensor is produced by arraying a plurality of back illuminated type of CCD image sensor chips, the sensor can be produced with a simple production process, the yield of the products in the production process can be enhanced, and the cost can be kept low. Particularly, in cases where the back illuminated type of CCD image sensor chips are arrayed in a zigzag pattern, free regions which are not occupied by the chips can be formed in the sensor, and electric circuits for pixel shift compensation and other elements can be located at the free regions.
In the thirteenth and fourteenth radiation image read-out methods and apparatuses in accordance with the present invention, the area sensor or the line sensor is employed as the photoelectric read-out means, and light detection is performed with a single simultaneous detection or successively with respect to lines. Therefore, the advantages over conventional radiation image read-out methods and apparatuses utilizing photoelectric read-out means, such as a photomultiplier, other than the line sensor can be obtained in that the time required to detect the emitted light can be kept short, the apparatus size can be reduced, and the cost can be kept low due to reduction in mechanical scanning optical parts, and the like.
With the fifteenth and sixteenth radiation image read-out methods and apparatuses in accordance with the present invention, the radiation image stored on the stimulable phosphor sheet is read out by utilizing the stimulating ray source constituted of the organic EL device. Therefore, the fifteenth and sixteenth radiation image read-out methods and apparatuses in accordance with the present invention are advantageous over radiation image read-out methods and apparatuses utilizing a fluorescent lamp, a cold cathode fluorescent lamp, or an LED array as the light source in that the intensity of the stimulating rays is high, sufficiently high luminance can be obtained, and therefore high stimulation energy can be imparted to the stimulable phosphor sheet. As a result, an image having a high signal-to-noise ratio can be obtained.
In cases where the light source is constituted of the organic EL device, by the formation of the organic EL device in a line-like shape or a surface-like shape, the line-like or surface-like EL light beam having a desired size can be produced by the organic EL device, and an light expanding mechanism may not be provided. Also, the directivity of the stimulating rays can be enhanced. Particularly, in cases where the line light source is constituted of the organic EL device, the advantages over a broad area laser capable of producing a laser beam of high luminance can be obtained in that the line light source is compact (thin), cheap, and easy to process.
With the fifteenth radiation image read-out method and apparatus in accordance with the present invention, wherein the line sensor comprises the plurality of the photoelectric conversion devices arrayed along each of the length direction of the linear light emitted by the stimulable phosphor sheet and the direction normal to the length direction, the same effects as those with the first radiation image read-out method and apparatus in accordance with the present invention can be obtained.
In the fifteenth and sixteenth radiation image read-out methods and apparatuses in accordance with the present invention, the area sensor or the line sensor is employed as the photoelectric read-out means, and light detection is performed with a single simultaneous detection or successively with respect to lines. Therefore, the advantages over conventional radiation image read-out methods and apparatuses utilizing photoelectric read-out means, such as a photomultiplier, other than the line sensor can be obtained in that the time required to detect the emitted light can be kept short, the apparatus size can be reduced, and the cost can be kept low due to reduction in mechanical scanning optical parts, and the like.
With the seventeenth radiation image read-out method and apparatus in accordance with the present invention, the light guiding optical system, which is colored and thereby imparted with the filter functions for transmitting only the emitted light and filtering out the stimulating rays, is located between the line light source and the line sensor. Therefore, it is not necessary for a particular filter for filtering out the stimulating rays to be inserted into the optical system. As a result, the distance between the stimulable phosphor sheet and the light guiding optical system can be reduced, and the light emitted by the stimulable phosphor sheet can be collected with a large angular aperture (numerical aperture).
Accordingly, the intensity and the position of the emitted light can be detected with a high light collecting efficiency and high resolution. As a result, an image having high sharpness can be obtained from the thus detected image signal.